<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function getSum(){
            let sum = 0;
            for(let i = 1;i <= 100;++i) sum += i;

            document.write('1加到100的和为:'+sum);
        }
        getSum();
    </script>
</body>
</html>